In U.S. Pat. No. 4,909,017 a method is disclosed for forming reclosable plastic bags wherein the zipper is disposed transverse with respect to the running direction of the web of bag film. One of the zipper profiles is attached to the bag web prior to the web being transformed into a bag tube while the other profile is connected to the bag web, at this point, only by the engagement of the interlocking elements of the profiles. This may be augmented by sealing the ends of the profile sections to each other. It is not until after the bag web is transformed into a tube that both of the profiles are sealed to the bag web.
A problem that is encountered with such transverse direction bag forming equipment is that as the web of bag film with attached transverse direction zipper segments passes over the forming collar (to begin its transformation from a flat sheet to a tube), the unattached profile tends to lift away from the attached profile. In the worst case, the profiles can become misaligned or separated thereby preventing a proper zipper bag from being formed.
It is the principle object of the present invention to provide a method for maintaining the zipper profiles, including the un-attached profile, on the bag film web as the web feeds to and through associated transverse direction bag making equipment.
A further object is to provide such a method without requiring any substantial additional equipment.
A still further object is to provide such a method which is readily adaptable to the numerous types of transverse direction zipper bag forming equipment that are now commercially available.
The above and other beneficial objects and advantages are attained in accordance with the present invention by providing a zipper segment for transverse direction application to a bag film web in which the profiles are of unequal lengths and joined together at their ends. As a result, the shorter profile is placed in tension. During bag formation the longer profile is initially attached to the bag film web and the shorter side is attached only by the engagement of the profile interlocking members and end seals. The shorter side, which is not directly attached to the web, nonetheless remains close to the web as a result of the tension imparted on the short side by the longer side.